linux-kernel - [PATCH 4/4] mm: vmscan: If kswapd has been running too long, allow it to sleep

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Message-Id: <1305295404-12129-5-git-send-email-mgorman@suse.de>
Date:	Fri, 13 May 2011 15:03:24 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	James Bottomley <James.Bottomley@...senPartnership.com>,
	Colin King <colin.king@...onical.com>,
	Raghavendra D Prabhu <raghu.prabhu13@...il.com>,
	Jan Kara <jack@...e.cz>, Chris Mason <chris.mason@...cle.com>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-ext4 <linux-ext4@...r.kernel.org>,
	Mel Gorman <mgorman@...e.de>
Subject: [PATCH 4/4] mm: vmscan: If kswapd has been running too long, allow it to sleep

Under constant allocation pressure, kswapd can be in the situation where
sleeping_prematurely() will always return true even if kswapd has been
running a long time. Check if kswapd needs to be scheduled.

Signed-off-by: Mel Gorman <mgorman@...e.de>
---
 mm/vmscan.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index af24d1e..4d24828 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2251,6 +2251,10 @@ static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
 	unsigned long balanced = 0;
 	bool all_zones_ok = true;
 
+	/* If kswapd has been running too long, just sleep */
+	if (need_resched())
+		return false;
+
 	/* If a direct reclaimer woke kswapd within HZ/10, it's premature */
 	if (remaining)
 		return true;
-- 
1.7.3.4

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